U.S. patent number 4,414,970 [Application Number 06/286,567] was granted by the patent office on 1983-11-15 for elastic bandages.
This patent grant is currently assigned to Smith and Nephew Associated Companies Limited. Invention is credited to Peter W. Berry.
United States Patent |
4,414,970 |
Berry |
November 15, 1983 |
Elastic bandages
Abstract
Moisture vapor transmitting elastic bandages which comprise an
inner layer of fabric and an outer layer of fabric bonded to a
central layer characterized in that the central layer comprises an
elastomeric film are described.
Inventors: |
Berry; Peter W. (Bishops
Stortford, GB2) |
Assignee: |
Smith and Nephew Associated
Companies Limited (GB)
|
Family
ID: |
26276389 |
Appl.
No.: |
06/286,567 |
Filed: |
July 24, 1981 |
Foreign Application Priority Data
|
|
|
|
|
Jul 30, 1980 [GB] |
|
|
8024855 |
Aug 27, 1980 [GB] |
|
|
8027719 |
|
Current U.S.
Class: |
602/75;
602/900 |
Current CPC
Class: |
A61F
13/00038 (20130101); A61F 13/023 (20130101); A61L
15/26 (20130101); A61L 15/42 (20130101); B32B
25/10 (20130101); A61F 13/00046 (20130101); A61F
13/08 (20130101); B32B 3/266 (20130101); B32B
27/12 (20130101); B32B 5/022 (20130101); B32B
27/40 (20130101); A61L 15/26 (20130101); C08L
75/04 (20130101); Y10S 602/90 (20130101); A61F
13/534 (20130101); A61F 13/537 (20130101); A61F
13/539 (20130101); A61F 2013/00102 (20130101); A61F
2013/00119 (20130101); A61F 2013/00263 (20130101); A61F
2013/00744 (20130101); A61F 2013/00876 (20130101); A61F
2013/15821 (20130101); A61F 2013/51447 (20130101); A61F
2013/530131 (20130101); A61F 2013/53445 (20130101); A61F
2013/53782 (20130101); A61F 2013/5395 (20130101) |
Current International
Class: |
A61F
13/02 (20060101); A61F 13/00 (20060101); A61L
15/42 (20060101); A61L 15/16 (20060101); A61L
15/26 (20060101); B32B 25/00 (20060101); B32B
25/10 (20060101); A61F 13/15 (20060101); A61L
015/00 () |
Field of
Search: |
;128/155,156,334R,169 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
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1535322 |
|
Apr 1970 |
|
DE |
|
482683 |
|
Apr 1938 |
|
GB |
|
895844 |
|
May 1962 |
|
GB |
|
1041792 |
|
Sep 1966 |
|
GB |
|
1167345 |
|
Oct 1969 |
|
GB |
|
1198391 |
|
Jul 1970 |
|
GB |
|
1367959 |
|
Sep 1974 |
|
GB |
|
1476894 |
|
Jun 1977 |
|
GB |
|
1568404 |
|
May 1980 |
|
GB |
|
1571049 |
|
Jul 1980 |
|
GB |
|
2056910 |
|
Mar 1981 |
|
GB |
|
1594587 |
|
Jul 1981 |
|
GB |
|
Primary Examiner: Yasko; John D.
Attorney, Agent or Firm: Jacobs & Jacobs
Claims
What we claim is:
1. A moisture vapour transmitting elastic bandage which comprises
an inner layer of fabric and an outer layer of fabric bonded to a
central layer, said central layer comprising an apertured
elastomeric film which allows the passage of wound exudate from the
inner layer to the outer layer and whereby the bandage has a
recoverable elastic strain in the length direction of 25% to 150%
at a stress of 180 g/cm.
2. An elastic bandage as claimed in claim 1 in which a fabric layer
is in a compressed state in the length direction.
3. An elastic bandage as claimed in claim 1 in which the central
layer comprises a polyurethane.
4. An elastic bandage as claimed in claim 1 in which a fabric layer
comprises an absorbent non-woven fabric.
5. An elastic bandage as claimed in claim 1 in which a fabric layer
comprises an integral thermoplastic net.
6. A method of making an elastic bandage of claim 1 which comprises
bonding an inner layer of fabric and an outer layer of fabric to a
central layer of apertured elastomeric film in a stretched
condition and thereafter allowing the composite to contract.
7. A method of making an elastic bandage of claim 5 which comprises
bonding a layer of integral thermoplastic net or net precursor
material to an apertured elastomeric film, stretching the laminate
in a longitudinal direction and thereafter allowing the laminate to
contract.
8. An elastic bandage according to claim 1 in which the apertured
film is an integral net.
9. A moisture vapour transmitting elastic bandage which comprises
an inner layer of fabric and an outer layer of fabric bonded by an
adhesive to a central apertured film layer, said bandage becoming
adhesive when stretched in a longitudinal direction by exposure of
the adhesive through the apertures.
10. An elastic bandage according to claim 1 in which the apertured
elastomeric film has 8 to 24 apertures per cm with a dimension of
0.1 to 1 mm.
11. An elastic bandage according to claim 8 in which the integral
net has longitudinal and transverse strands.
12. An elastic bandage according to claim 1 in which the bandage
has an initial bandaging stress of 140 g/cm to 230 g/cm.
Description
The present invention is concerned with elastic bandages and
methods of their manufacture.
Elastic bandages in adhesive and non-adhesive form are used inter
alia to provide support and to assist in the healing of strained
muscles and in the treatment of various venous conditions where it
is important to maintain a level of compressive force for
considerable periods of time.
Known elastic bandages have employed crimped yarns, high twist
cotton yarns or elastic threads. Elastic woven bandages containing
crimped yarns have relatively poor elastic properties. Elastic
woven bandages containing high twist cotton yarns which are shrunk
during processing are expensive to manufacture and also have
relatively poor elastic properties which can be badly affected by
moisture. Elastic bandages formed by weaving elastic warp threads
under tension into a woven structure have good elastic properties
but are expensive to produce and can cause local constriction at
the location of individual threads.
British Patent Specification No. 895,844 discloses an air permeable
elastic bandage which consists of two outer layers of foam bonded
to an intermediate layer of reinforcing fabric. The use of foam
layers can avoid the problems of local constriction by providing
the bandage with uniform elastic properties over the width of the
bandage. However, it is difficult to design and manufacture an
elastic bandage with good reproducible elastic compression
properties without using foam layers which are comparatively thick
in relation to the thickness of the fabric layers. Thick foam
layers would also increase the bulk of the elastic bandages.
A class of elastic bandages have now been discovered that have good
elastic properties which can be uniform over the width of the
bandage. These new bandages also offer the advantage of being
relatively easy to manufacture.
The present invention provides a moisture vapour transmitting
elastic bandage which comprises an inner layer of fabric and an
outer layer of fabric bonded to a central layer characterised in
that the central layer comprises an elastomeric film.
The fabric may be woven or non-woven. It is preferred to use
non-woven fabrics in the bandages of this invention.
The use of a non-woven fabric in elastic bandages of the invention
can provide a desirable textile `feel` to the surface of the
bandage. Additionally use of an absorbent non-woven fabric can
provide the bandage with a degree of absorbency for water and body
fluids such as blood.
Another preferred fabric is an integral thermoplastic net.
The term `integral thermoplastic net` means a thermoplastic net
formed with junctures integral with the strands of the net, for
example thermoplastic nets formed by extrusion or by biaxially
stretching an embossed sheet. Such nets are effectively
non-elastic.
In this specification the term `non-woven fabric` does not include
integral thermoplastic nets.
The use of an integral thermoplastic net can provide the elastic
bandages of the invention with a bandage surface which has abrasion
resistance in both dry and moist conditions. Advantageously in
adhesive elastic bandages of the invention the net bandage surface
can act as an effective adhesive release surface which may allow
the adhesive bandage to be easily unrolled without the need to
employ expensive interleaving adhesive protectors.
Integral thermoplastic nets can be made in different forms which
can provide elastic bandages of this invention with additional
advantages hereafter described.
The moisture vapour transmitting elastic bandage of the invention
can have a number of alternative constructions. A favoured elastic
bandage construction consists of two layers of non-woven fabric
bonded to a central layer of an elastomeric continuous film as
hereinafter described.
Another favoured elastic bandage construction consists of an outer
layer of integral thermoplastic net and an inner layer of absorbent
non-woven fabric bonded to a central layer of elastomeric
continuous film.
It is desirable that the bandage of this invention should have a
sufficient level of moisture vapour transmission to prevent
maceration of the skin or a `clammy feeling` due to the build up of
moisture under the bandage. It is therefore desirable that the
bandage should have a moisture vapour transmission rate of at least
150 g, more suitably at least 350 g and preferably at least 500
g/cm.sup.2 /24 hours at 37.degree. C. at 100%-10% relative humidity
difference.
The moisture vapour transmission rate may be measured by the Payne
Cup method. The method uses a cup 1.5 cm deep with a flanged top.
The inner diameter of the flange is such to provide an area for
moisture vapour transmission of 10 cm.sup.2. In this method 10 ml
of distilled water is added to the cup and a sample of the material
under test, large enough to completely cover the flange, is clamped
over the cup. The complete assembly is then weighed and placed in a
cabinet where the temperature and relative humidity are maintained
at 37.degree. C. and 10% respectively. After 17 hours the cup is
removed from the cabinet and allowed to cool at room temperature.
After re-weighing, the mass of water lost by vapour transmission is
calculated and the result expressed as in g/m.sup.2 /24 hr at
37.degree. C., 100%-10% relatively humidity difference.
It follows from the nature of the product that the fabric layers of
elastic bandages of the invention will be extensible in the length
direction of the bandage. Preferred extensible fabric layers are in
a compressed state in the length direction.
Another aspect of this invention provides a moisture vapour
transmitting elastic bandage of the invention in which a layer of
fabric is in a compressed state in the length direction.
Another desirable aspect of this invention provides a moisture
vapour transmitting elastic bandage in which a layer of non-woven
fabric is in a compressed state in the length direction.
A particularly desirable aspect of this invention provides a
moisture vapour transmitting elastic bandage in which a layer of
integral thermoplastic net is in a compressed state in the length
direction.
The compressed state of the fabric layer in the length direction
can take several different forms which can be present in elastic
bandages of this invention.
In one form the fabric layer is wrinkled into lines of corrugation
or ridges transverse to the width of the bandage. In another form
only localised regions of the fabric are wrinkled for example the
flexible strands between the rigid junctures of a net can be
deformed by folding or twisting. In yet another form the fabric
layer is compressed from its open form to a closed form, for
example a net with diamond shaped apertures in open state can be
compressed into a net with slit apertures and vice versa. The
compressed state of the fabric in the length direction often
results from the preferred methods of making the elastic bandages
of the invention as hereinafter described. Alternatively the fabric
can be in a compressed state before it is bonded to the elastomeric
film layer. Suitable fabrics of this type include creped or crimped
fabrics for example micro creped paper.
An elastic bandage of this construction has the advantage that
fabric provides the bandage in a stretch state with a stop which
limits the amount by which the bandage can be stretched and thus
provides the bandage with a maximum bandaging stress. Thus, by the
proper selection of materials and the degree of compression in the
longitudinal direction of the fabric it is possible to make an
elastic bandage which has the desired stress/strain characteristics
including if necessary limits to the bandaging stress and the
recoverable elastic strain.
It has now been found that an initial bandaging stress of
approximately 90 g to 270 g/cm width (0.5 to 1.5 lb per inch width)
more suitably 140 g to 230 g/cm width (0.8 to 1.3 lb per inch
width) and preferably 180 g/cm width (1 lb per inch width) is
desirable especially for the treatment of venous insufficiency of
the leg. It is also desirable that the bandage should have
sufficient recoverable strain at that stress to cope with the
shrinkage of the bandaged area during treatment, for example the
reduction of swelling during treatment of venous insufficiency of
the leg.
It is desirable that the bandage should have a recoverable elastic
strain in the length direction of at least 25% more suitable at
least 50% desirably at least 75% and preferably at least 100% at a
stress of 180 g/cm width (1 lb per inch width). Generally a
recoverable elastic strain of more than 150% at a stress of 180
g/cm width (1 lb per inch width) is not required.
It is also desirable that the bandage should maintain a compressive
stress on the area under the bandage, for example legs where in
time the combination of a reduction in swelling and stress decay
can understandably reduce the compressive stress of the
bandage.
The elastomeric film present in the bandage of this invention
provides the bandage with its desirable elastic properties. The
elastomeric film can be continuous, macroporous or microporous.
However, it is preferred that the elastomeric film in the bandage
of this invention is continuous as this can produce a bacterial
barrier which is desirable if infected areas are to be covered.
Therefore in another aspect the present invention provides a
moisture vapour transmitting elastic bandage which comprises an
inner layer of fabric and an outer layer of fabric bonded to a
central layer characterised in that the central layer comprises a
continuous elastomeric film.
Suitable films which may be obtained in continuous form and which
transmit moisture vapour can be made from polyurethane, for example
a thermoplastic polyurethane.
Certain preferred films are those made from the so-called `Estanes`
(Registered Trade Mark) of B. F. Goodrich Co. Ltd. Estanes are a
range of thermoplastic polyester and polyether urethanes. A
particularly apt film forming material is Estane 5714 which is a
polyether urethane. Estane 5714 is described in `Properties and
Processing of Estane Polyurethane Materials` published by B. F.
Goodrich August 1968.
The thickness and weight of the film used in the bandage of this
invention can vary according to elastic and moisture vapour
transmission properties required in the final bandage.
Suitable film thicknesses will generally be in the range 12.5.mu.
to 75.mu. (0.005 to 0.003 inch) and more aptly 20.mu. to 50.mu.
(0.0008 inch to 0.002 inch). Films of Estane 5714 have been found
to be particularly suitable when 25.mu. (0.001 inch) thick at which
thickness the film has a moisture vapour transmission rate of
1800/m.sup.2 /22 hours at 37.degree. C. at 100%-10% relative
humidity difference.
Optionally additives such as fillers, antioxidants or the like may
be mixed into the film material before it is formed into a film.
The addition of a filler such as silica (for example 5% Gasil
(Trade Mark)) may be advantageous.
The suitable polyurethane films can be formed by casting from
solution or by hot melt coating or extrusion in conventional
manner.
The elastomeric film of the elastic bandages of the invention can
have apertures. Elastic bandages with a central layer of apertured
film will have high moisture vapour transmission rates. The
bandages may also have increased capacity to absorb wound exudate
if the excess exudate from an inner absorbent layer in contact with
the wound can pass through the film apertures to an outer absorbent
layer.
Therefore in a further aspect the present invention provides a
moisture vapour transmitting elastic bandage which comprises an
inner layer of fabric and an outer layer of fabric bonded to a
central layer characterised in that the central layer comprises an
apertured elastomeric film.
The number and size of the aperture in the apertured film may be
sufficient to allow wound exudate to pass the film to an outer
absorbent layer. Suitable apertured elastomeric films have
apertures with a dimension of from 0.05 mm to 2.5 mm more
preferably from 0.1 mm to 1 mm. Suitable apertured films have a
thickness of 0.025 mm to 2.5 mm and preferably 0.05 mm to 0.15 mm.
The apertured elastomeric film can be in any convenient form such
as a perforated film or net.
In a favoured aspect of the invention the apertured elastomeric
film is an integral net. The term `integral net` means a net in
which the strands and junctures are formed integrally during
manufacture.
The elastomeric integral net of the elastic bandage of the
invention can have any convenient form depending on the chosen
arrangement of strand, juncture and hole areas and also their
shapes and relative size.
In a preferred form the net consists of essentially of longitudinal
and transverse strands to give a square grid hole pattern. Suitable
nets of this type aptly have 4 to 40 apertures per cm and
preferably 8 to 24 apertures per cm in both longitudinal and
transverse directions.
Square grid pattern elastomeric integral nets of the elastic
bandages of the invention may have transverse strands which are
thicker than the longitudinal strands to provide a better
resistance to `necking` when the bandage is stretched in the
longitudinal direction.
Normally the apertured elastomeric films are made of
pharmaceutically acceptable water insoluble elastomer. Suitable
elastomers include thermoplastic polymers of polyurethane,
polybutadiene and butadiene-styrene block copolymers.
Preferred grades of thermoplastic polyurethanes are Estane
polyurethanes as described hereinbefore in relation to continuous
films.
A suitable polyurethane net is disclosed in U.S. Pat. No.
3,913,510.
The non-woven fabric used in a fabric layer of the bandages of this
invention will generally have a weight of from 10 gsm to 80 gsm and
more aptly from 12 gsm to 60 gsm, for example 18 gsm to 45 gsm.
The non-woven fabric employed may aptly have absorbent
properties.
Suitable non-woven fabrics include those made from cellulosic
fibres such as viscose rayon fibres, or other flexible
material.
Preferred non-woven fabrics for use include apertured non-woven
fabrics such as those made from bonded viscose filaments. A
suitable fabric of this kind is available as Bemliese (Trade Mark)
from Asahai Chemical Industry Co. Bemliese is available in weights
ranging from 18-45 gsm which are particularly suitable for use in
this invention. The Bemliese fabric has diamond shaped apertures
arranged in staggered rows in the longitudinal direction. The
fabric can be stretched in the transverse direction due to the
ability of the aperture to change its shape from an open diamond to
a slit in the transverse direction. A non-woven fabric of this
structure has some ability to accommodate the change in dimensions
of the fabric, depending on the degree of compression, when the
non-woven fabric is in a compressed state.
The use of this or similar net-like non-woven fabric can provide a
bandage which has a recoverable elastic strain in both longitudinal
and transverse directions and has a surface appearance which is
flat.
The integral thermoplastic nets should be sufficiently flexible to
enable the net to be in a compressed state in the length direction
when the bandage is in the unstretched condition.
The layer of integral thermoplastic net provides reinforcement for
and modifies the elastic properties of the elastomeric film layer
to give the desirable properties of the elastic bandages of the
invention.
Suitable nets include nets made by biaxial stretching thermoplastic
sheets embossed with a pattern of on one or both sides raised
bosses, discrete cavities, parallel ribs and grooves or mixtures
thereof. Process of making these nets are described in British
Patent Specification Nos. 914,489, 1,055,963, 1,075,487, 1,110,051,
1,496,786 and 1,531,715.
A preferred integral thermoplastic net has sufficient rigidity in
the transverse direction to resist the tendency of the elastic
bandage to `neck in` when stretched in a longitudinal
direction.
A particularly apt integral thermoplastic net is a net ref. Y218
available from Smith & Nephew Plastics Ltd., Hull, U.K. The
Y218 net is made by longitudinally stretching a high density
polyethylene sheet embossed with a pattern of raised hexagon
shapped bosses in a staggered arrangement. Y218 net has rows of
approximately 10 per cm packed bosses in the transverse direction
and approximately 4 per cm bosses in the length direction connected
by flexible oriented strands. British Patent Specification No.
1,055,963 discloses suitable methods of making such nets.
The elastic bandage of this invention may be non-adhesive,
self-adhesive or coated with a moisture vapour transmitting
pressure sensitive adhesive. An adhesive elastic bandage can have a
peelable protector, for example a silicone release coated paper, on
an adhesive surface to enable a bandage in roll form to be easily
unrolled.
The pressure sensitive adhesive coating (in adhesive bandages of
this invention) can be in any convenient form. The adhesive may be
discontinuous. Alternatively, the adhesive may be continuous.
The adhesive can be present on one or both of the outer surfaces of
adhesive bandage of the invention.
Normally and preferably the pressure sensitive adhesive is
continuous. Most aptly the adhesive has a moisture vapour
transmission rate of at least 250 g and preferably at least 500
g/m.sup.2 /24 hrs at 37.degree. C. at 100%-10% relative humidity
difference. Suitable pressure sensitive adhesives which transmit
moisture vapour as a continuous coat include various acrylate ester
copolymers, polyvinyl ethyl ether and polyurethane adhesive.
Examples of suitable adhesives are given in U.K. Specification No.
1,280,631. The pressure sensitive adhesives can be polymers per se,
blends of polymers, mixtures of polymers with tackifying resins
optionally other materials such as fillers and antioxidants.
A preferred pressure sensitive adhesive comprises a blend of high
and low viscosity polyvinyl ethyl ethers in particular `adhesive
composition A` disclosed in British Patent Specification No.
1,280,631. Other preferred pressure sensitive adhesives comprise
copolymers of acrylate ester with acrylic acid for example as
disclosed in British Patent Application No. 2070631 and in
particular a copolymer of 47 parts by weight of n-butylacrylate, 47
parts by weight of ethylhexyl acrylate and 6 parts by weight of
acrylic acid polymerised in acetone according to the general method
given in U.S. Pat. No. 2,884,126 and with an intrinsic viscosity of
at least 1.9 dl/g.
The weight range of the adhesive coating is generally from 15 to 70
gsm and preferably from 20 to 45 gsm. The adhesive coating can be
formed by any convenient method including solution and emulsion
coating, coating from a hot melt and by extrusion.
It has been found that certain non-adhesive elastic bandages of the
invention as hereafter described become adhesive when stretched
longitudinally.
In yet a further aspect the invention provides a moisture vapour
transmitting elastic bandage which comprises an inner layer of
fabric and an outer layer of a fabric bonded to a central layer
characterised in that the bandage becomes adhesive when stretched
in a longitudinal direction by exposure of the adhesive used to
bond a fabric layer to to the central film layer.
A favoured elastic bandage of this type comprises an integral
thermoplastic net, typically net reference Y218 from Smith and
Nephew Plastics Limited, bonded to a central layer of elastomeric
film by a pressure sensitive adhesive. The non-adhesive bandage
becomes adhesive when stretched due to the exposure of the pressure
sensitive adhesive through the apertures of the net. A preferred
elastic bandage has a layer of net bonded to both sides of the
central layer of elastomeric film by a pressure sensitive
adhesive.
In another aspect the invention provides a method of making an
elastic bandage by bonding two layers of fabric to a central layer
of elastomeric film in a stretched condition and thereafter
allowing the composite to contract.
The elastic bandage of the invention using a net layer or layers
can be made by two alternative processes. Both processes involve
stretching the elastomeric film in a longitudinal direction. In one
process the net layer is bonded to the elastomeric layer before
stretching. In the second process the net layer is bonded to the
elastomeric layer after stretching. A combination of these two
processes is also possible.
In another aspect the invention provides a method of making a
moisture vapour transmitting elastic bandage by bonding a layer of
integral thermoplastic net to an elastomeric film in a stretched
condition and thereafter allowing the composite to contract.
In another aspect the invention provides a method of making
moisture vapour transmitting elastic bandages which comprises
bonding a layer of integral thermoplastic net or net precursor
material to an elastomeric film stretching the laminate in a
longitudinal direction and allowing the laminate to contract.
A net precursor material is a material which will form an integral
thermoplastic net when stretched in a longitudinal direction.
Preferred net precursor materials are embossed thermoplastic sheets
described hereinbefore which have been given a stretch in the
transverse direction.
Preferred net precursor materials are disclosed in British Patent
Specification No. 1531715. Suitably apt net precursor materials are
described in Examples 1 and 2 of British Patent Specification No.
1531715. These net precursor materials can be given a longitudinal
stretch in the region of 100% to 200% to form open nets. A
longitudinal stretch in the region of 10% to 50% will give
partially opened nets or net precursor material which are also
suitable for the process of this invention.
It is desirable that the precursor net material can be stretched at
least 50%, more suitable 75% and preferably at least 100% in the
longitudinal direction before breaking.
The bonding may be effected in any convenient manner such as by
heat sealing or the use of an adhesive such as a solvent
adhesive.
It is preferred that the fabric layers are bonded to the
elastomeric film by means of an adhesive. Suitable adhesives for
use include hot melt adhesives, solvent adhesives, pressure
sensitive adhesives, and contact adhesives.
The adhesive coating or layer can transmit moisture vapour.
Suitable moisture vapour transmitting pressure sensitive adhesives
are those described hereinbefore for the adhesive coating on the
external surface of the adhesive form of the bandage.
The pressure sensitive adhesive employed at a weight of from 5-50
gsm and preferably from 10-30 gsm.
In the process of making the bandage it is desirable that the
elastomeric film is stretched in a longitudinal direction.
It is preferred that the elastomeric film is longitudinally
stretched under biaxial stress conditions to limit the amount by
which the film contracts in the transverse direction, for example
by longitudinally stretching the film over rollers. Elastic
bandages made by this process when stretched longitudinally will
contract less in the transverse direction (that is `neck` less)
than elastic bandages made by a process where the elastomeric film
is stretched in `free flight` without lateral restraint. The amount
of stretch will depend on the recoverable elastic strain required
in the bandage.
It is desirable that the film should be stretched by at least 75%
and preferably by at least 100% during manufacture.
If two layers of non-woven fabric are used to form the elastic
bandage of the invention it is preferred that the two layers are
bonded to the stretched film in the same operation.
FIGS. 1, 2 and 3 illustrate processes for manufacturing bandages of
the invention.
In FIG. 1 a laminate 1 of an elastomeric film coated on both sides
with a pressure sensitive adhesive and protected on both sides with
a release paper is fed in pressure contact between the nip of two
rotating rollers 2 and the release paper 3 and 4 removed. The
adhesive coated elastomeric film 5 is passed under pressure through
the nip of rollers 6 which are rotating at a surface speed faster
than rollers 4 so that film 5 is in a stretched condition. The film
5 is bonded to non-woven fabrics 7 and 8 which are fed
simultaneously into the nip. The resulting laminate 9 is then wound
onto roller 10, which is rotating at a surface speed similar to
that of rollers 2. The bandage sheet 9 thus contracts under low
tension. The bandage sheet is thereafter cut into individual
bandages.
FIG. 2 illustrates an alternative process for making a bandage of
the invention in which the pressure sensitive adhesive is
pre-coated onto one side of each of the non-woven fabric layers
instead of on both sides of the elastomeric film. This process has
the advantage that the surfaces of the elastomeric film are
non-tacky during the stretching stage thus preventing the film
sticking to the rollers.
In FIG. 2 elastomeric film 11 is passed between the nip of rollers
12 and then between the nip rollers 13 rotating at a surface speed
faster than that of rollers 12 where the elastomeric film is
stretched longitudinally and laminated to pressure sensitive
adhesive coated thermoplastic net 14 fed into the nip of rollers
13. The resultant laminate sheet is wound onto roller 16 rotating
at a surface speed similar to that of rollers 12. The sheet 15 is
thus allowed to contract under low tension.
Another layer of adhesive coated fabric is then laminated to the
other side of the elastomeric film laminate by the same process.
Alternatively, another layer of adhesive coated fabric can be
laminated to the other side of the elastomeric film simultaneously
with net layer 14 by passage through nip rollers 13. The bandage
sheet is thereafter cut into individual bandages.
In FIG. 3 a bonded laminate 17 of net precursor material and the
elastomeric film is fed between nip rollers 18 and is then
stretched longitudinally by passage through nip rollers 19 rotating
at a surface speed faster than that of rollers 18 to form a sheet
20 of a net bonded to an elastomeric film. Sheet 20 is then wound
onto roller 21 which is rotating at a surface speed similar to that
of rollers 18 so that the sheet 20 is allowed to contract under low
tension.
A second net precursor layer is then laminated to the elastomeric
film side of sheet 20 and the laminate subjected to a second
stretching and contracting process to form a bandage sheet. The
bandage sheet is thereafter cut into individual bandages.
In an alternative and preferred process of making the bandage
sheet, sheet 17 can be a bonded laminate of an elastomeric film
between an inner and outer layer of net precursor material. This
process enables the bandage sheet to be formed in a single
stretching and contracting process.
In a second alternative process of forming the bandage sheet an
adhesive coated non-woven fabric is laminated to the elastomeric
film side of sheet 17 by passage between the nip of rollers 19 in
similar manner to that illustrated in FIG. 2.
EXAMPLE 1
A 10 cm.times.10 cm.times.0.025 mm thick film of Estane 5714
containing 5% Gasil filler was coated on both sides by a knife over
flat bed coating unit with 33% solids solution in acetone of an
acrylate ester copolymer adhesive and dried in an oven at
80.degree. C. to give a dry coating weight on both sides of the
film of 12 gsm. The adhesive was a copolymer of 47 parts by weight
n-butyl acrylate, 47 parts by weight of ethylhexyl acrylate, 6
parts by weight of acrylic acid having an intrinsic viscosity of
1.9. The coated film was stretched by 100% to give a film 20 cm
long.times.7 cm wide and an 18 gsm apertured Bemliese non-woven
fabric bonded to both sides under pressure. The stretched laminate
was allowed to contract free of tension to a bandage speed 10.5 cm
long.times.9.3 cm wide.
The bandage of the Example had the following properties:
(i) Moisture vapour transmission rate: 1600 g/m.sup.2 /24 hrs at
37.degree. C. at 100%-10% RH difference.
(ii) Strain at 180 g/cm width (1 lb per inch width) stress: 80%
(iii) Weight: 140 gsm.
The bandage of this Example also had a recoverable elastic strain
in the transverse direction. The non-woven fabric surfaces of the
bandage were in a flat compressed state. A surprising feature of
the bandage was that a 180 g/cm stress can be obtained with 100%
strain in longitudinal direction whereas the same stress in a
25.mu. (0.001 inch) Estane 5714 film requires a strain of not less
than 500%.
EXAMPLE 2
A 10 cm.times.10 cm.times.0.025 mm thick film of Estane 5714
containing 5% Gasil filler was coated on both sides by a knife over
flat bed coating unit with 33% solids solution in acetone of an
acrylate ester copolymer adhesive and dried in an oven at
80.degree. C. to give a dry coating weight on both sides of the
film of 12 gsm. The adhesive was a copolymer of 47 parts by weight
of n-butyl acrylate, 47 parts by weight of ethyl hexyl acrylate and
6 parts by weight of acrylic acid having an intrinsic viscosity of
1.9. The coated film was stretched by 100% to give a film 20 cm
long by 7 cm wide and an 18 gsm apertured Bemliese non-woven fabric
bonded to one side and a net ref. Y218 from Smith and Nephew
Plastics Limited bonded to the other side under pressure. The
stretched laminate was allowed to contract free of tension to form
the product.
The resulting bandage did not `neck in` at a 72% strain and had 72%
strain at 180 g/cm inch width (1 lb per inch) stress.
The bandage of this example did not possess significant adhesive
properties in the unstretched form but when stretched exhibited
adhesive properties.
EXAMPLE 3
A 10 cm.times.10 cm coated Estane 5714 film was prepared as Example
1. A net precursor material of Example 1 of British Patent
Specification No. 1531715 was bonded to both sides of the coated
film. The laminate was stretched by 135% to give a length of 23.5
cm and the stretched laminate allowed to contract free of tension
to form the product.
The bandage did not `neck in` at 70% strain and had 70% strain at a
stress of 180 g/cm inch width (1 lb per inch).
EXAMPLE 4
A 10 cm.times.10 cm coated Estane 5714 film was prepared as Example
1. A net precursor material of Example 1 of British Patent
Specification No. 1531715 was laminated under pressure to one side
of the coated film. The laminate was stretched by 100% to give a
length of 20 cm and an 18 gsm Bemliese non-woven fabric laminated
to the exposed adhesive side of the stretched laminate. The
stretched laminate was allowed to contract free of tension to form
the product.
The resulting bandage did not `neck in` at a 42% strain and had a
42% strain at a 180 g/cm inch width (1 lb per inch) stress.
EXAMPLE 5
An adhesive elastic bandage was made by laminating under pressure,
by passage through nip rollers, the bandage sheet of Example 1 and
a silicone coated release paper (Steralease 67 available from
Sterling Coated Papers Limited) coated with the acrylic copolymer
adhesive (30 gsm) of Example 1. The bandage sheet laminate was
wound into a roll with the siilicone coated release paper acting as
a protector for the adhesive coating to form an adhesive elastic
bandage. The silicone paper protector can be removed before or
during the application of the adhesive bandage to the patient.
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